1. Field of the Invention
The invention relates to a circuit breaker that incorporates a monitor providing an indication of line conditions such as surges and the cause of a trip such as a thermal trip, magnetic trip, arc fault trip or ground fault trip.
2. Background Information
A type of circuit breaker commonly used in residential and light commercial applications typically has a thermal/magnetic trip unit. This well known trip unit includes a bimetal that deflects in response to a persistent overload condition to actuate an operating mechanism that opens the separable contacts of the circuit breaker. A magnetic armature is attracted by the larger overcurrent caused by, for instance, a short circuit to also actuate the operating mechanism. There is no indication; however, as to which condition caused the circuit breaker to trip.
It is now common to incorporate electronic trip circuits in these breakers with thermal/magnetic trip units to provide protection against arc faults and ground faults. U.S. Pat. No. 5,546,266 discloses a circuit breaker of this type with light emitting diodes to provide a visual indication that a trip was caused by an arc fault or ground fault, as appropriate. However, it is not possible to identify a trip as caused by an overload or an overcurrent.
Some larger circuit breakers that utilize electronic circuits, now typically implemented by a microprocessor, to provide overload and overcurrent protection similar to that provided by the thermal/magnetic trip unit, have light emitting diodes distinguishing these two types of trips. For instance, U.S. Pat. No. 5,926,355 discloses such a circuit breaker that also has light emitting diodes to identify ground faults and short delay trips in addition to the thermal or long delay trip and an instantaneous or magnetic trip.